JP-A-61-7577 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a positive electrode having a protective layer comprising a substance having electron conductivity combined with ionic conductivity (e.g., lithium ion conductivity), giving an oxide of tungsten, molybdenum or vanadium as a preferred example of the substance having electron and ion conductivity. However, the compounds enumerated have not achieved sufficient effects in preventing internal short-circuits.
JP-A-4-28173 discloses providing a polymer film which selectively transmits an alkali metal ion on the surface of a negative electrode made of an alkali metal or an alkali metal alloy countering to a positive electrode. However, use of such a porous polymer film is fraught with the problem that the battery capacity may be greatly reduced.
Accordingly, an object of the present invention is to improve productivity in the production of a nonaqueous secondary battery having a high discharge voltage, satisfactory charge and discharge cycle characteristics, and excellent safety.